Set image settings for each individual File Output Node, in the Python API
You can actually set the settings for each individual node.
Create your node:
file_output_node = tree.nodes.new('CompositorNodeOutputFile')

Then you can set your settings for this node by going into the format attribute. For example:
file_output_node.format.file_format = &quot;PNG&quot; # default is &quot;PNG&quot;
file_output_node.format.color_mode = &quot;RGB&quot;  # default is &quot;BW&quot;
file_output_node.format.color_depth = &quot;16&quot;  # default is 8
file_output_node.format.compression = 0     # default is 15